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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Sat Oct 11, 2008 12:29 pm Post subject:
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Sorry, I can see how that could be a little unclear.
It could be simulated a million different ways from SPICE to C code. I chose Mathworks Simulink because that's what I'm using at the moment.
The circuit doesn't need a DAC whether its built in hardware or software. What it does need is an analog mixer to change the ratio/mix of the Walsh functions.
I've only made the saw and sine since those are the coefficients I have. They sound good, better than you'd expect from a "4-bit" equivalent. I haven't done much musical with them, just test tones. I didn't research or think/test enough what the input pulse wave input has to be for a given output frequency so I didn't play chromatic notes. Doing a simulation with MIDI input and some knobs to control the function ratios would probably take more work than putting it in hardware, so I'm not sure I'll get any useful demos up (other than "4-bit" sine and sawtooth at fixed frequency if you'd like). |
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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Sat Oct 11, 2008 12:35 pm Post subject:
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You could filter or slew limit the output of a Walsh generator but that would be missing the point a little I think. The extra harmonics from the quantization steps should be useful in a musical filtering context, running the output through your favorite filter as opposed to a fixed filter to "smooth" the waveform.
Things I have to look into are how musical or useful is the outputs if you sweep the coefficient values by twisting the knobs on the mixer and how precise do the mixing ratios have to be to achieve a proper sine or saw output for example. |
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aerogramma
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 13
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Posted: Wed Oct 15, 2008 4:36 am Post subject:
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jnuaury wrote: | theres two ways to do this
one follows the concept of bit depth and the other is similar to sampling rates
"bit depth" method
you use a divider and make a "dac" with resistors after a square wave to get a sine wave essentially with a bit depth of however many divisions you use
also youll need to clock the square wave at a muh higher frequency than the pitch you want to be the sine-ish wave
link
http://www.robthefiddler.com/electronics-audio-diy/circuit-experiments/big-johnson-signal-generator/
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thanks! I like the bith depth method...
I don't have a 4018 (the Johnson counter) right now can anyone suggest a substitute?
aero |
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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Wed Oct 15, 2008 12:06 pm Post subject:
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Wow the Johnson generator has similar results to a Walsh generator but is much simpler. |
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richardc64
Joined: Jun 01, 2006 Posts: 679 Location: NYC
Audio files: 26
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Posted: Wed Oct 15, 2008 12:44 pm Post subject:
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I found this http://home1.gte.net/res0658s/fatman/4069_lfo.html , from our own ScottG, who admits it isn't quite a sinewave. Still, you can get two from a single 4069. _________________ Revenge is a dish best served with a fork... to the eye |
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Sun Nov 16, 2008 11:20 am Post subject:
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Or you can build one oscillator and follow it with linear amplifier stages in the same IC to make a better sinewave output.
Note that with a smaller capacitor, this LFO becomes an audio oscillator - not voltage controlled, but at least knob controlled. And the same use for extra gates applies for an audio oscillator too - you can follow the S-shape triangle output of the bare oscillator with some linear amplifier gain stages which will further S shape the waveform making it more sinelike.
The secret to a good sinewave output using this method is to play with the gain of and the number of linear amplifier stages used. _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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aerogramma
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 13
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Posted: Thu Apr 09, 2009 9:25 am Post subject:
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[deleted!] Last edited by aerogramma on Thu Apr 09, 2009 9:32 am; edited 1 time in total |
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aerogramma
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 13
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Posted: Thu Apr 09, 2009 9:30 am Post subject:
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[deleted] |
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aerogramma
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 13
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fluxmonkey
Joined: Jun 24, 2005 Posts: 708 Location: cleve
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aerogramma
Joined: Feb 27, 2008 Posts: 156 Location: Roma, Italy - London, UK
Audio files: 13
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Posted: Wed Aug 19, 2009 8:14 am Post subject:
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indeed, maybe just easier to understand for me ...
so perhaps this time i'll be able to make it do something ... |
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DGTom
Joined: Dec 08, 2008 Posts: 211 Location: Adelaide
Audio files: 3
G2 patch files: 1
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Posted: Fri Aug 28, 2009 5:52 pm Post subject:
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This 4018 cct. is pretty cool.
might have to try one with a 4017, or some other counters, got some 4029s yesterday... Binary or Decade sine wave!?
When I first breadboarded it I just croc clipped one of my existing lunetta oscs. in, one of my Tom Bugs 40106s... I discovered by feeding the clock input with an oscillator that is synced to another osc. produces some very slimy tones! I replaced the 10uf with a 2.2uf, which brought a few harmonics back but the level drop isn't so bad, 10uf makes the signal drop right off.
This is a problem I've hit a few time w/ my lunetta.. need to figure out a decent way to boost and/or build some passive attens in for all the bastard loud squarewaves in other modules!
I also got it running pretty nice with synthmongers simple 2n3904 / 40106 VCO. |
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picsynth
Joined: Oct 16, 2008 Posts: 27 Location: New Zealand
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Posted: Sun Sep 20, 2009 6:42 pm Post subject:
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Don Lancaster describes simple sine wave generators in his CMOS Cookbook. He uses a 4018 walking ring counter and some resistors. The Cookbook contains tables of resistor values for different resolution sine waves.
You could then run through a low pass filter to remove any higher harmonics.
I haven't tried this circuit but it sounds like a great idea. |
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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
Audio files: 3
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Posted: Thu Sep 24, 2009 3:05 am Post subject:
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I'm surprised nobody said anything about using multiple binary/decade counters with their outputs summed together through an R2R ladder. This would create a high resolution sine (or any waveform really).
I haven't tried it but it should work right? You may need to use quite a few counters in order to eliminate a lot or most aliasing artifacts though. I kind of like that 'digital' sounding wave form.
I was planning on making some sort of module that takes a square wave input and outputs a saw/sine/tri wave using this technique. Each waveform would have it's on "reset" aka sync and other goodies. _________________ Youtube!
modular demos!
Whacky tunes! |
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Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
G2 patch files: 1
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Posted: Thu Sep 24, 2009 6:21 am Post subject:
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Hey Synthmonger,
You should do a search for my "ReAnimator". Very closely related to what you're talking about. You might be able to solve the problem I got bogged down on. _________________ What makes a space ours, is what we put there, and what we do there. |
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slabman
Joined: Sep 01, 2005 Posts: 102 Location: UK
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Posted: Fri Sep 25, 2009 3:01 pm Post subject:
commutating filter |
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I guess, in theory, you could also clock a switched capacitor filter at a high frequency, and crank up the resonance till it oscillates? I imagine there'd be some aliasing though |
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FredM
Joined: Nov 17, 2007 Posts: 2 Location: U.K.
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Posted: Sat Jun 26, 2010 6:44 pm Post subject:
Re: SINE wave from CMOS? Subject description: any advice on how to get one? |
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aerogramma wrote: | Hello!
i've been building my first CMOS based devices in the last weeks and had a lot of fun... and probably avoided to go bankrupt too
I really like the rawness that comes out but I'm also an indestructable SINE wave lover
Is there a simple way to get a sine wave from a CMOS IC?
thanks and all the best from here
aero
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you can get close by using an XOR and mixing two high frequencies - this provides a PWM-like string of pulses which, when integrated, get close to sine (they actually correspond to a triangle waveform)..
See: http://www.element-14.com/community/groups/theremin-general-resources
and more specifically Digital Heterodyning.pdf - link: http://www.element-14.com/community/docs/DOC-16892/l/digital-heterodyningpdf |
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